#include<iostream>
#include<sstream>
using namespace std;
int main()
{
  char str[20];
  stringstream MM("温柔了岁月");
  MM >> str;
  cout << str;
  cout << MM.str() << endl;
  MM.str(""); //清除
  //整数转变成字符型 to_string()强转
  string buf = to_string(124);
  int number = 1203;
  char arr1[29];
  stringstream arr2(arr1);
  arr2 << number;
  arr2 >> arr1;
  cout << arr1;
  //字符型转整数
  stringstream arr3("123");
  int number2 = 0;
  arr3 >> number2;
  cout << number2 << endl;  
}

#include<iostream>
#include<sstream>
#include<iomanip>
using namespace std;
int main()
{
  //数据分割(流中默认空格  作为单一数据的间隔)
  stringstream str1("ip: 192.168.1.1");
  char arr1[20];
  str1 >> arr1;
  char str2;
  int number[4];
  str1 >> number[0];
  str1 >> str2;
  str1 >> number[1];
  str1 >> str2;
  str1 >> number[2];
  str1 >> str2;
  str1 >> number[3];
  for (auto& v : number)
  {
    cout << v << setw(10);
  }
  system("pause");
  return 0;
}

判断文件是否打开成功

include<fstream>
using namespace std;
int main()
{
  fstream file("test.text", ios::in | ios::out | ios::trunc);
  //等效下面两行代码
  fstream file2;
  file2.open("text", ios::in | ios::out | ios::trunc);
  //判断文件打开方法一
  if (!file)
  {
    cerr << "打开文件失败" << endl;
  }
  //判断文件打开方法二
  if (!file.is_open())
  {
    cerr << "打开失败" << endl;
  }
  system("pause");
  return 0;
}

#include<iostream>
#include<iomanip>
#include<fstream>
#include<string>
using namespace std;
class MM
{
public:
  MM(){}
  MM(string name,int age,string sex): name(name),age(age),sex(sex) {}
  void print()
  {
    cout << name << setw(5) << age << setw(5) << sex << endl;
  }
  void Savefile(string filename)
  {
    fstream file(filename, ios::in | ios::out | ios::trunc);
    if (!file)
    {
      cerr << "打开文件失败" << endl;
    }
    file << name << setw(5) << age << setw(5) << sex << endl;
    file.close();
  }
  void read(string filename)
  {
    fstream file(filename, ios::in);
    if (!file)
    {
      cerr << "打开文件失败" << endl;
      return;
    }
    file >> this->name >> this->age >> this->sex;
    file.close();
  }
private:
  string name;
  int age;
  string sex;
};
int main()

void charway(string readfile, string writefile)
  {
    fstream read1(readfile, ios::in);
    fstream write1(writefile, ios::out);
    while (!read1.eof())  //eof()字符的末尾
    {
      char key = read1.get();
      write1.put(key);
    }
    read1.close();
    write1.close();
  }

void bianry(string readfile, string writefile)
  {
    fstream read(readfile, ios::in | ios::binary);
    fstream write(writefile, ios::out | ios::binary);
    while (!read.eof())
    {
      char arr1[200];
      read.read(arr1, 200);
      write.write(arr1, 200);
    }
    read.close();
    write.close();
  }

//文件指针移动 -->计算文件的大小
  int test(string file)
  {
    fstream read(file, ios::in | ios::binary);
    read.seekg(0, ios::end);
    int size = read.tellg();
    read.close();
    return size;  
  }